This wasn't a stupid question. I can repeat this "MPG gauge bug" at will on a certain hill on the way home from work. I have owned an 04 HCH, and trust me, this is a BUG in the 06 HCH. But, I guess this is one of those "first redesigned year" glitches that is to be expected. There will probably be a software update in a few months to correct it.